Human skin is a complex organ which extends over the entire body. There are different types of skin at different portions of the body. For example, facial skin is different from that of the scalp, and even the skin on the palm of the hand is different than that on the back of the hand. Although the type of skin can vary over a person's body, skin is generally composed of two main layers of tissue. The epidermis, the outermost layer, is composed of several layers. The dermis, also called corium or cutis vera, is composed of a papillary layer above and a reticular layer below.
The human epidermis is principally composed of keratinocytes but contains also other types of cells including the melanocytes and the Langerhans' cells. Each of these cell types contribute, through their specific function, to the essential role played by the skin.
The dermis provides a solid support for the epidermis. It is also its feeder layer. The dermis consists mainly of fibroblasts but leukocytes, mast cells or tissue macrophages are also present. The dermis further contains blood vessels and nerve fibers. The acellular part (i.e., the area in between the cells) of the dermis is called extracellular matrix. The extracellular matrix of skin is composed of various extracellular components including proteins; in particular collagen fibers and elastin. Other extracellular matrix components of skin include glycosaminoglycans (e.g., hyaluronic acid, chondroitin sulfate, dermatan sulfate, keratan sulfate, heparan sulfate, etc.), proteoglycans (e.g., fibromodulin, decorin, biglycan, perlecan, heparan sulfate proteoglycan 2, agrin, versican, aggrecan, lumican, collagen type IX, collagen type XII, collagen type XIV, testican 1, testican 2, etc.) and various glycoproteins (e.g., fibrillin 1, thrombospondin-1 and -2, tenascin-C and -X, osteopontin, fibronectin, laminin-5 and -6, vitronectin, etc.). These extracellular components are synthesized by dermal fibroblasts, which make dermal fibroblasts the primary constituent in the structural assembly of the dermis.
The extracellular matrix is a highly heterogeneous amalgam of morphologically diverse architectural entities. It organizes and imparts structural integrity to individual tissues, in addition to modulating cell behavior by interacting with cell surface receptors and soluble growth factors. Dysfunctions and changes in components of the extracellular matrix can therefore interfere with both tissue integrity and cell performance. Dysfunctions and changes in components of the extracellular matrix of skin and mucosa in humans can lead to skin aging, skin atrophy, damaged skin, wounded skin, atrophy of vulva and vagina (vulvovaginal atrophy), or to any other conditions, disorders and diseases of skin and mucosa associated with changes in extracellular matrix components.
Therefore, a need exists in the art for compositions having improved activity that maintain or even increase the level of a rather large number of extracellular matrix components, including those that are altered in aged, damaged, wounded, atrophic skin, atrophy of vulva and vagina, or in any other conditions, disorders and diseases of skin and mucosa in humans associated with changes in extracellular matrix components.